Small animal imaging initiatives are growing rapidly due to the enormous potential for improved understanding and treatment of human disease through animal imaging. At present, every radiologic modality available for use in humans has been adapted for small animal use. Other modalities have been devised solely for the purpose of in vivo imaging of research animals. As investigators increasingly make use of small animal imaging, the need for improved and standardized animal handling technology is critical. Our research goal is to create and distribute animal handling systems that are robust, safe, easy to use, and able to provide high-quality radiological images across multiple imaging platforms including MRI, CAT, PET and SPECT. The Specific Aims are to (1) Test and improve a stereotaxic rodent holder for rat and mouse head imaging, (2) Test and enhance animal monitoring and physiological support for the modular animal handling system, and (3) Evaluate the ability to use the rodent holder in multi-modality imaging applications. This proposed research is the result of a partnership between a small business specializing in the manufacture of animal handling devices (ASI Instruments, Inc.) and a university based research team (Neurobiological Magnetic Resonance Imaging Laboratory, Department of Neuroscience, Georgetown University). This industry/academic partnership will merge of the technology of stereotaxic instrumentation, typically used for the precise anatomical alignment needed in surgical procedures, and the technology of radiological imaging, in order to precisely align small animals to the orthogonal imaging planes of medical imaging equipment. Knowledge gained from this Phase I study will be used in Phase II for developing animal holders for other animals and for purposes other than imaging the brain of these animals (e.g. skeletal muscle, spinal cord, heart, lung, etc.).